This invention relates to an expander primarily intended for use in expanding tubing downhole.
It has been proposed to use a roller expander to expand slotted and solid tubing in drilled bores, and in particular in oil and gas wells, such are described in, for example, WO 00/37767, WO 00/37768 and WO 00/37771. A typical roller expander comprises a body carrying a number of radially movable rollers. The rollers may be mounted on pistons or cones such that elevated internal fluid pressure or axial force may be applied to she expander to urge the rollers radially outwardly into contact with a surrounding expandable tube. By simultaneously rotating and advancing the expander a length of tubing may be expanded from a first diameter to a larger second diameter.
It is among the objectives of embodiments of the present invention to provide an improved roller expander for use in such applications.
According to a first aspect of the present invention there is provided a tubing expander comprising a body carrying at least one radially movable expansion member and a sleeve mounted about the body and being radially supported by the expansion member.
The invention also relates to a method of expanding tubing comprising the steps:
providing a tubing expander comprising a body carrying at least one radially movable expansion member and a sleeve mounted about the body and being radially supported by the expansion member;
locating the expander in a tubing section of a first diameter;
radially extending the expansion member to urge a portion of the sleeve into contact with an internal surface of the tubing section; and
rotating the expander such that the sleeve is rolled around the internal surface of the tubing section and expands the tubing section to a larger second diameter.
The invention has particular application in expansion of slotted expandable tubing, in which an unexpanded tubing section features a plurality of overlapping axial slots. Expansion of the tubing is accommodated, at least in part, by bending of the fingers or webs of material between the slots, such that in the expanded tubing the slots assumed a diamond shape. With conventional roller expanders, featuring generally cylindrical rollers or balls mounted around an expander body, the relatively small diameter rollers or balls tend to drop into the slots, that is as the expander rotates and a ball encounters a slot, the ball will be pushed outwardly into the slot and must then be pushed inwardly out of the slot, against the ball actuating force, to allow the ball to move past the slot. The circumference of a typical slotted tube may feature nine slots, and when an expander is being rotated within such a pipe at, for example, 250 rpm, the expander and string will experience a degree of vibration. However, in the present invention the sleeve has a relatively large diameter, such that the sleeve will not drop into the slots to the same extent, the sleeve will tend to bridge the slots, such that the rotating expander experiences less vibration and requires a lower torque to rotate the expander. Of course the expander may be utilise to expand other forms of tubing, including but not limited to solid-walled tubulars, tubulars with other slot patterns, tubulars with holes of a variety of sizes and patterns, tubulars with purposely machined or cast xe2x80x9cdefectsxe2x80x9d, such as zones of thinned wall, and tubulars which have been longitudinally folded or corrugated into various forms.
Although reference is made above to a tubing section of a first diameter, the invention is not limited to use in tubulars which are initially cylindrical, and as noted above may be utilised in one or both of the unfolding and radial expansion of tubulars which have been longitudinally folded or corrugated into various forms. Further, the invention may be used independently or in combination with other unfolding or expansion tools, devices or mechanisms.
The portion of the tubing section subject to deformation may be relatively short, for example to create a patch or straddle, or to create a hanger or a seal. Alternatively, the tubing section may be of considerable length.
Preferably, the expander comprises a plurality of radially movable expansion members and associated sleeves. In a preferred embodiment, four sets of expansion members and sleeves are provided. Adjacent expansion members Are preferably circumferentially offset. In a preferred embodiment, a first set of two adjacent expansion members are mutually offset by 180xc2x0, and a second set of two members are mutually offset by 180xc2x0 and the first and second sets are offset by 90xc2x0. Conveniently, the leading sleeve features a tapered leading end, and may be relatively long. The other sleeves may also feature tapered leading ends. The diameter of the sleeves may increase from the leading end of the expander. Of course particular applications of the expander may require or benefit from the provision of particular numbers of sets of sleeves and members, particular sleeve configurations, and particular expansion member offsets.
The sleeve axis may be adapted to remain parallel to the axis of the tubing section as the sleeve rotate. In such an arrangement it is necessary to apply an external axial force to move the expander axially through the tubing section. Alternatively, the sleeve axis may be skewed relative to the axis of the tubing section, in which case the rotating sleeve, in contact with the tuning section, will act in a similar manner to a screw thread and thus induce an axial force on the expander, minimising or obviating the requirement, to apply an axial force to advance the expander. The outer surface of the sleeve may define a contact surface, such as a helical profile or screw thread, to facilitate creation and transfer of axial force.
Preferably, the expansion member comprise pistons mounted in corresponding blind recesses in the expander body. The recesses may communicate with an axial fluid passage in the body. Conveniently, the recesses are cylinders, facilitating cutting of the cylinders in the body. Most preferably, the expansion members further comprise rollers mounted on piston-mounted axles. Preferably, the axles extend axially of the expander body.
Preferably, the body defines a leading end dimensioned to be a snug fit in the tubing section to be expanded, to stabilize the expander in the tubing